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AUTHOR COMMENTARIES - From Special Topics

Biofuels - August 2008
Interview Date: August 2008
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Knothe Dr. Gerhard Knothe
From the Special Topic of Biofuels
According to our Special Topics analysis of biofuels research over the past decade, the work of Dr. Gerhard Knothe ranks at #3 by total number of papers, at #11 by total cites, and at #12 by cites/paper. These rankings are based on 18 qualifying papers cited a total of 229 times.

In Essential Science IndicatorsSM from Thomson Reuters, Dr. Knothe's record includes a Highly Cited Paper in the field of Engineering: "Exhaust emissions of biodiesel, petrodiesel, neat methyl esters, and alkanes in a new technology engine," (Knothe G, Sharp CA, Ryan TW, Energ. Fuel. 20[1]: 403-8, January-February 2006).


Dr. Knothe is a Research Chemist in the Food and Industrial Oil Research unit of the USDA's National Center for Agricultural Utilization Research in Peoria, Illinois. In 2006, he received the Industrial Uses of Soybeans Award from the United Soybean Board and the American Oil Chemists' Society. He is also a co-editor of The Biodiesel Handbook (AOCS Press, 2005).

In the interview below, ScienceWatch.com talks with Dr. Knothe about his biofuels research.

  Please tell us a little about your research and educational background.

My research is mainly concerned with the use of vegetable oils and their derivatives as alternative diesel fuels and related aspects. My educational background is in chemistry, specifically a Ph.D. in organic polymer chemistry.

  What first interested you in biofuels research?

"...I would like to see a biodiesel fuel with optimized properties becoming available or at least that its realization will be in the near future."

Prior to joining the National Center for Agricultural Utilization Research, which at that time was still known as the Northern Regional Research Center, I had had no professional exposure to biofuels research, except for having heard about it. I found and still find the perspective of working in this area intriguing.

  Your most-cited original paper in our biofuels Special Topic is the 2005 Fuel Processing Technology paper, "Dependence of biodiesel fuel properties on the structure of fatty acid alkyl esters," (86[10]: 1059-70, 25 June 2005)." Would you sum up the major points of this paper for our readers?

This paper summarizes and evaluates several important fuel properties—for example, cetane number, viscosity, and oxidative stability—that are determined by the major components of biodiesel, i.e., alkyl esters of fatty acids. By combining insights on the various properties, it points in a direction for the improvement of biodiesel fuel properties by modifying the fatty ester composition of biodiesel.

This work has been modified and expanded by a recent publication entitled "'Designer' biodiesel: Optimizing fatty ester composition to improve fuel properties," (Energy & Fuels 22[2]: 1358-64, March-April 2008). To summarize the new paper briefly, while methyl oleate overall possesses good fuel properties, esters of palmitoleic acid or decanoic acid may be even more preferable for biodiesel.

  Another key paper is your 2006 Energy & Fuels article, "Exhaust emissions of biodiesel, petrodiesel, neat methyl esters, and alkanes in a new technology engine." Would you talk a little about the aims, methods, and findings in this project?

This work had the objective to adapt previous findings on the influence of various fatty acid chains on exhaust emissions to a newer technology diesel engine, thus providing additional insights on structure-property relationships. Ultra-low sulfur diesel (ULSD) fuels had become a salient issue so it was also straightforward to compare how fatty acid alkyl esters influence emissions in comparison to straight-chain alkanes, which are enriched in ULSD and are their "ideal" components. The heavy-duty exhaust emissions testing was conducted at Southwest Research Institute.

The results showed that biodiesel and its components slightly increased NOx emissions, as had been known from previous literature, but reduced particulate matter emissions considerably more than the neat alkanes, which may favorably affect the exhaust emissions control technologies needed when using biodiesel as a fuel.

  Are there any other papers, regardless of citations, that you feel are important to your field, and if so, what are they and why are they important?

"I found and still find the perspective of working in this area intriguing."

The perspectives of other researchers and one’s own perspective can differ significantly on such issues. In any case, I hope that the other work on fuel properties regarding issues such as cetane numbers, lubricity, and viscosity, as well as analytical work on methods such as NIR and NMR are important and interesting.

  Where do you see your research going in five to ten years?

Niels Bohr (and maybe other individuals) has been quoted as saying that "Prediction is very difficult, especially about the future" and who would not agree? That aside, I would like to see a biodiesel fuel with optimized properties becoming available or at least that its realization will be in the near future. And I hope that the work described in my papers and future work will eventually help achieve that goal.

  What should the "take-away lesson" about your work be for the general public?

Promising work is ongoing to provide "better" biofuels, in this case biodiesel.

Gerhard Knothe, Ph.D.
United States Department of Agriculture
Agricultural Research Service
National Center for Agricultural Utilization Research
Peoria, IL, USA

  Dr. Gerhard Knothe's current most-cited paper in Essential Science Indicators, with 13 cites:
Knothe G, Sharp CA, Ryan TW, "Exhaust emissions of biodiesel, petrodiesel, neat methyl esters, and alkanes in a new technology engine," Energ. Fuel. 20(1): 403-8, Jan-Feb 2006. Source: Essential Science Indicators from Thomson Reuters.

Keywords: biodiesel, vegetable oils, fuel properties, cetane number, viscosity, oxidative stability, fatty esters, exhaust emissions, petrodiesel, neat methyl esters, alkanes.

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Special Topics : Biofuels : Gerhard Knothe